1. Field of the Invention
This invention relates to a technical field covering display devices (hereinafter called light-emitting devices) comprising, on a substrate, an element (hereinafter called light-emitting element) having a structure comprising an anode, a cathode, and a thin film (hereinafter called light-emitting layer) sandwiched between the anode and the cathode to emit light relying upon a phenomenon called electroluminescence). The invention further relates to a technical field covering an apparatus for producing the above light-emitting device.
2. Description of the Related Art
In recent years, it has been urged to develop a light-emitting device called organic EL panel and organic light-emitting diode (OLED) as video displays. This is realized by generating a light-emitting phenomenon called electroluminescence by recombining positive holes and electrons in the light-emitting layer formed between an electrode (hereinafter called anode) for injecting positive holes and an electrode (hereinafter called cathode) for injecting electrons, and by controlling on/off of light emission to display images.
The light-emitting element which plays the most important role in the light-emitting devices includes the light-emitting layer (particularly, the light-emitting layer comprising an organic compound) which is very weak against oxygen and moisture, is easily degraded and, must, hence, be fabricated with utmost care. Namely, technology is required for carrying out a series of processes from the formation of an anode (or a cathode), formation of a light-emitting layer, up to the formation of the cathode (or the anode) followed by sealing (for intimately sealing the light-emitting element) keeping off the atmosphere. Therefore, the apparatus for producing the light-emitting devices tends to become bulky requiring an increased floor area (so-called footprint).
The production apparatus having a large foot print is accompanied by a difficulty in laying out the clean room and, further, becomes considerably heavy. Therefore, a very high cost is required for designing the clean room. At present, however, the film-forming device and the sealing device have simply been coupled together in the form of a multi-chamber still leaving much room for development from the standpoint of decreasing the size and reducing the weight as a production apparatus.
At present further, a method has been vigorously developed for forming the light-emitting layer used for the light-emitting device by applying a solution, such as by a spin-coating method, an ink jet method or a printing method. In particular, formation of a thin organic film by the ink jet method is already approaching a practicable level, and its basic technology has been disclosed in, for example, JP-A-10-12377.
The ink jet method is technology accomplished by applying the ink jet system that has heretofore been used in the printers to the formation of thin films, by using, instead of an ink, a solvent such as water or an alcohol in which is dissolved or dispersed a solute that is a material of the organic thin film, and applying a droplet solution to each of the pixels. When the ink jet method is used, the size of the apparatus can be decreased since no vacuum device is required. When constructed in the form of a multi-chamber, however, the apparatus as a whole becomes inevitably bulky.